Methods of forming group III piezoelectric thin films via removal of portions of first sputtered material

ABSTRACT

A method of forming a piezoelectric thin film includes sputtering a first surface of a substrate to provide a piezoelectric thin film comprising AlN, AlScN, AlCrN, HfMgAlN, or ZrMgAlN thereon, processing a second surface of the substrate that is opposite the first surface of the substrate to provide an exposed surface of the piezoelectric thin film from beneath the second surface of the substrate, wherein the exposed surface of the piezoelectric thin film includes a first crystalline quality portion, removing a portion of the exposed surface of the piezoelectric thin film to access a second crystalline quality portion that is covered by the first crystalline quality portion, wherein the second crystalline quality portion has a higher quality than the first crystalline quality portion and processing the second crystalline quality portion to provide an acoustic resonator device on the second crystalline quality portion.

CROSS-REFERENCE TO RELATED APPLICATIONS AND CLAIM FOR PRIORITY

The present application claims priority to and is a divisional of U.S.patent application Ser. No. 16/742,202; titled “METHODS OF FORMING GROUPIII PIEZOELECTRIC THIN FILMS VIA REMOVAL OF PORTIONS OF FIRST SPUTTEREDMATERIAL” filed Jan. 14, 2020 which claims priority to U.S. ProvisionalPatent Application Ser. No. 62/887,126 entitled “METHODS OF FORMINGGROUP III PIEZOELECTRIC THIN FILMS VIA REMOVAL OF PORTIONS OF FIRSTSPUTTERED MATERIAL,” filed in the U.S.P.T.O, on Aug. 15, 2019, and is acontinuation-in-part application of U.S. patent application Ser. No16/513,143 entitled “METHODS OF FORMING GROUP III PIEZOELECTRIC THINFILMS VIA SPUTTERING,” filed in the U.S.P.T.O, on Jul. 16, 2019, whichwas a continuation-in-part application of U.S. patent application Ser.No. 15/784,919 titled “PIEZOELECTRIC ACOUSTIC RESONATOR MANUFACTUREDWITH PIEZOELECTRIC THIN FILM TRANSFER PROCESS,” filed Oct. 16, 2017 (nowU.S. Pat. No. 10,355,659 which issued on Jul. 16, 2019), the disclosuresof which are all incorporated herein by reference in their entireties.

The present application incorporates by reference, for all purposes, thefollowing concurrently filed patent applications, all commonly owned:U.S. patent application Ser. No. 14/298,057 titled “RESONANCE CIRCUITWITH A SINGLE CRYSTAL CAPACITOR DIELECTRIC MATERIAL”, filed Jun. 6, 2014(now U.S. Pat. No. 9,673,384 issued Jun. 6, 2017), U.S. patentapplication Ser. No. 14/298,076 titled “ACOUSTIC RESONATOR DEVICE WITHSINGLE CRYSTAL PIEZO MATERIAL AND CAPACITOR ON A BULK SUBSTRATE”, filedJun. 6, 2014 (now U.S. Pat. No. 9,537,465 issued Jan. 3, 2017), U.S.patent application Ser. No. 14/298,100 titled “INTEGRATED CIRCUITCONFIGURED WITH TWO OR MORE SINGLE CRYSTAL ACOUSTIC RESONATOR DEVICES”,filed Jun. 6, 2014 (now U.S. Pat. No. 9,571,061 issued Feb. 14, 2017),U.S. patent application Ser. No. 14/341,314 titled “WAFER SCALEPACKAGING”, filed Jul. 25, 2014, U.S. patent application Ser. No.14/449,001 titled “MOBILE COMMUNICATION DEVICE CONFIGURED WITH A SINGLECRYSTAL PIEZO RESONATOR STRUCTURE”, filed Jul. 31, 2014 (now U.S. Pat.No. 9,716,581 issued Jul. 25, 2017), and U.S. patent application Ser.No. 14/469,503 titled “MEMBRANE SUBSTRATE STRUCTURE FOR SINGLE CRYSTALACOUSTIC RESONATOR DEVICE”, filed Aug. 26, 2014.

BACKGROUND

The present invention relates generally to electronic devices. Moreparticularly, the present invention provides techniques related to amethod of manufacture and a structure for bulk acoustic wave resonatordevices, single crystal bulk acoustic wave resonator devices, singlecrystal filter and resonator devices, and the like. Merely by way ofexample, the invention has been applied to a single crystal resonatordevice for a communication device, mobile device, computing device,among others.

Wireless data communications can utilize RF filters operating atfrequencies around 5 GHz and higher. It is known to use Bulk acousticWave Resonators (BAWR) incorporating polycrystalline piezoelectric thinfilms for some applications. While some polycrystalline basedpiezoelectric thin film BAWRs may be adequate for filters operating atfrequencies from about 1 to 3 GHz, applications at frequencies around 5GHz and above may present obstacles due to the reduced crystallinityassociated with such thin poly-based films.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a simplified diagram illustrating an acoustic resonatordevice having topside interconnections according to an example of thepresent invention.

FIG. 1B is a simplified diagram illustrating an acoustic resonatordevice having bottom-side interconnections according to an example ofthe present invention.

FIG. 1C is a simplified diagram illustrating an acoustic resonatordevice having interposer/cap-free structure interconnections accordingto an example of the present invention.

FIG. 1D is a simplified diagram illustrating an acoustic resonatordevice having interposer/cap-free structure interconnections with ashared backside trench according to an example of the present invention.

FIGS. 2 and 3 are simplified diagrams illustrating steps for a method ofmanufacture for an acoustic resonator device according to an example ofthe present invention.

FIG. 4A is a simplified diagram illustrating a step for a methodcreating a topside micro-trench according to an example of the presentinvention.

FIGS. 4B and 4C are simplified diagrams illustrating alternative methodsfor conducting the method step of forming a topside micro-trench asdescribed in FIG. 4A.

FIGS. 4D and 4E are simplified diagrams illustrating an alternativemethod for conducting the method step of forming a topside micro-trenchas described in FIG. 4A.

FIGS. 5 to 8 are simplified diagrams illustrating steps for a method ofmanufacture for an acoustic resonator device according to an example ofthe present invention.

FIG. 9A is a simplified diagram illustrating a method step for formingbackside trenches according to an example of the present invention.

FIGS. 9B and 9C are simplified diagrams illustrating an alternativemethod for conducting the method step of forming backside trenches, asdescribed in FIG. 9A, and simultaneously singulating a seed substrateaccording to an embodiment of the present invention.

FIG. 10 is a simplified diagram illustrating a method step formingbackside metallization and electrical interconnections between top andbottom sides of a resonator according to an example of the presentinvention.

FIGS. 11A and 11B are simplified diagrams illustrating alternative stepsfor a method of manufacture for an acoustic resonator device accordingto an example of the present invention.

FIGS. 12A to 12E are simplified diagrams illustrating steps for a methodof manufacture for an acoustic resonator device using a blind viainterposer according to an example of the present invention.

FIG. 13 is a simplified diagram illustrating a step for a method ofmanufacture for an acoustic resonator device according to an example ofthe present invention.

FIGS. 14A to 14G are simplified diagrams illustrating method steps for acap wafer process for an acoustic resonator device according to anexample of the present invention.

FIGS. 15A-15E are simplified diagrams illustrating method steps formaking an acoustic resonator device with shared backside trench, whichcan be implemented in both interposer/cap and interposer free versions,according to examples of the present invention.

FIGS. 16A-16C through FIGS. 31A-31C are simplified diagrams illustratingvarious cross-sectional views of a single crystal acoustic resonatordevice and of method steps for a transfer process using a sacrificiallayer for single crystal acoustic resonator devices according to anexample of the present invention.

FIGS. 32A-32C through FIGS. 46A-46C are simplified diagrams illustratingvarious cross-sectional views of a single crystal acoustic resonatordevice and of method steps for a cavity bond transfer process for singlecrystal acoustic resonator devices according to an example of thepresent invention.

FIGS. 47A-47C though FIGS. 59A-59C are simplified diagrams illustratingvarious cross-sectional views of a single crystal acoustic resonatordevice and of method steps for a solidly mounted transfer process forsingle crystal acoustic resonator devices according to an example of thepresent invention.

FIG. 60 is a flowchart illustrating methods of forming a highcrystallinity piezoelectric thin film by removal of a portion of thethin film that is first formed on the substrate, for inclusion indevices shown, for example, FIGS. 8-9A, 22-23, 39-40, 52-53 in someembodiments according to the invention.

FIG. 61 is a schematic illustration of a sputtering chamber that can beused to form the high crystallinity piezoelectric thin films on thesubstrate using a Group III target material (such as Al, Sc, or Al andSc) in a plasma environment where the substrate may be optionally heatedto a relatively high sputtering temperature as shown, for example, inFIGS. 60 and 64 in some embodiments according to the invention.

FIG. 62 is a cross-sectional view illustrating a piezoelectric thin filmsputtered directly onto the substrate which may be processed as shown,for example, in FIGS. 60 and 64 in some embodiments according to theinvention.

FIG. 63 is a cross-sectional view illustrating a piezoelectric thin filmsputtered directly onto a seed layer on the substrate which may beprocessed as shown, for example, in FIGS. 60 and 64 in some embodimentsaccording to the invention.

FIG. 64 is a flowchart illustrating methods of forming a highcrystallinity piezoelectric thin film on a heated substrate at arelatively high sputtering temperature followed by removal of a portionof the thin film that is first formed on the substrate, for inclusion indevices shown, for example, FIGS. 8-9A, 22-23, 39-40, 52-53 in someembodiments according to the invention.

FIG. 65 is a graph illustrating an improvement of about 5% in animpedance of an acoustic resonator as a function of frequency, includinga piezoelectric thin film (AlScN) formed by removing about a 500Angstrom portion from the surface that was first formed on the substratein some embodiments according to the invention compared to aconventionally formed piezoelectric thin film.

FIG. 66 is a graph illustrating an improvement of about 21% in a Qfactor of an acoustic resonator as a function of frequency, including apiezoelectric thin film (AlScN) formed by removing about a 500 Angstromportion from the surface that was first formed on the substrate in someembodiments according to the invention compared to a conventionallyformed piezoelectric thin film.

DETAILED DESCRIPTION OF EMBODIMENTS ACCORDING TO THE INVENTION

According to the present invention, techniques generally related toelectronic devices are provided. More particularly, the presentinvention provides techniques related to a method of manufacture andstructure for bulk acoustic wave resonator devices, single crystalresonator devices, single crystal filter and resonator devices, and thelike. Merely by way of example, the invention has been applied to asingle crystal resonator device for a communication device, mobiledevice, computing device, among others.

FIG. 1A is a simplified diagram illustrating an acoustic resonatordevice 101 having topside interconnections according to an example ofthe present invention. As shown, device 101 includes a thinned seedsubstrate 112 with an overlying single crystal piezoelectric layer 120,which has a micro-via 129. The micro-via 129 can include a topsidemicro-trench 121, a topside metal plug 146, a backside trench 114, and abackside metal plug 147. Although device 101 is depicted with a singlemicro-via 129, device 101 may have multiple micro-vias. A topside metalelectrode 130 is formed overlying the piezoelectric layer 120. A top capstructure is bonded to the piezoelectric layer 120. This top capstructure includes an interposer substrate 119 with one or morethrough-vias 151 that are connected to one or more top bond pads 143,one or more bond pads 144, and topside metal 145 with topside metal plug146. Solder balls 170 are electrically coupled to the one or more topbond pads 143.

The thinned substrate 112 has the first and second backside trenches113, 114. A backside metal electrode 131 is formed underlying a portionof the thinned seed substrate 112, the first backside trench 113, andthe topside metal electrode 130. The backside metal plug 147 is formedunderlying a portion of the thinned seed substrate 112, the secondbackside trench 114, and the topside metal 145. This backside metal plug147 is electrically coupled to the topside metal plug 146 and thebackside metal electrode 131. A backside cap structure 161 is bonded tothe thinned seed substrate 112, underlying the first and second backsidetrenches 113, 114. Further details relating to the method of manufactureof this device will be discussed starting from FIG. 2 .

FIG. 1B is a simplified diagram illustrating an acoustic resonatordevice 102 having backside interconnections according to an example ofthe present invention. As shown, device 101 includes a thinned seedsubstrate 112 with an overlying piezoelectric layer 120, which has amicro-via 129. The micro-via 129 can include a topside micro-trench 121,a topside metal plug 146, a backside trench 114, and a backside metalplug 147. Although device 102 is depicted with a single micro-via 129,device 102 may have multiple micro-vias. A topside metal electrode 130is formed overlying the piezoelectric layer 120. A top cap structure isbonded to the piezoelectric layer 120. This top cap structure 119includes bond pads which are connected to one or more bond pads 144 andtopside metal 145 on piezoelectric layer 120. The topside metal 145includes a topside metal plug 146.

The thinned substrate 112 has the first and second backside trenches113, 114. A backside metal electrode 131 is formed underlying a portionof the thinned seed substrate 112, the first backside trench 113, andthe topside metal electrode 130. A backside metal plug 147 is formedunderlying a portion of the thinned seed substrate 112, the secondbackside trench 114, and the topside metal plug 146. This backside metalplug 147 is electrically coupled to the topside metal plug 146. Abackside cap structure 162 is bonded to the thinned seed substrate 112,underlying the first and second backside trenches. One or more backsidebond pads (171, 172, 173) are formed within one or more portions of thebackside cap structure 162. Solder balls 170 are electrically coupled tothe one or more backside bond pads 171-173. Further details relating tothe method of manufacture of this device will be discussed starting fromFIG. 14A.

FIG. 1C is a simplified diagram illustrating an acoustic resonatordevice having interposer/cap-free structure interconnections accordingto an example of the present invention. As shown, device 103 includes athinned seed substrate 112 with an overlying single crystalpiezoelectric layer 120, which has a micro-via 129. The micro-via 129can include a topside micro-trench 121, a topside metal plug 146, abackside trench 114, and a backside metal plug 147. Although device 103is depicted with a single micro-via 129, device 103 may have multiplemicro-vias. A topside metal electrode 130 is formed overlying thepiezoelectric layer 120. The thinned substrate 112 has the first andsecond backside trenches 113, 114. A backside metal electrode 131 isformed underlying a portion of the thinned seed substrate 112, the firstbackside trench 113, and the topside metal electrode 130. A backsidemetal plug 147 is formed underlying a portion of the thinned seedsubstrate 112, the second backside trench 114, and the topside metal145. This backside metal plug 147 is electrically coupled to the topsidemetal plug 146 and the backside metal electrode 131. Further detailsrelating to the method of manufacture of this device will be discussedstarting from FIG. 2 .

FIG. 1D is a simplified diagram illustrating an acoustic resonatordevice having interposer/cap-free structure interconnections with ashared backside trench according to an example of the present invention.As shown, device 104 includes a thinned seed substrate 112 with anoverlying single crystal piezoelectric layer 120, which has a micro-via129. The micro-via 129 can include a topside micro-trench 121, a topsidemetal plug 146, and a backside metal 147. Although device 104 isdepicted with a single micro-via 129, device 104 may have multiplemicro-vias. A topside metal electrode 130 is formed overlying thepiezoelectric layer 120. The thinned substrate 112 has a first backsidetrench 113. A backside metal electrode 131 is formed underlying aportion of the thinned seed substrate 112, the first backside trench113, and the topside metal electrode 130. A backside metal 147 is formedunderlying a portion of the thinned seed substrate 112, the secondbackside trench 114, and the topside metal 145. This backside metal 147is electrically coupled to the topside metal plug 146 and the backsidemetal electrode 131. Further details relating to the method ofmanufacture of this device will be discussed starting from FIG. 2 .

FIGS. 2 and 3 are simplified diagrams illustrating steps for a method ofmanufacture for an acoustic resonator device according to an example ofthe present invention. This method illustrates the process forfabricating an acoustic resonator device similar to that shown in FIG.1A. FIG. 2 can represent a method step of providing a partiallyprocessed piezoelectric substrate. As shown, device 200 includes a seedsubstrate 110 with a piezoelectric layer 120 formed overlying. In aspecific example, the seed substrate can include silicon, siliconcarbide, aluminum oxide, or single crystal aluminum gallium nitridematerials, or the like. The piezoelectric layer 120 can include apiezoelectric single crystal layer or a thin film piezoelectric singlecrystal layer.

As appreciated by the present inventors, a high crystallinitypiezoelectric thin film 120 may be formed on the substrate 110 bysputtering a Group III target material (such as Al, Sc, or Al and Sc,and other materials) in a plasma environment and subsequently removingthe first formed portion of the piezoelectric thin film 120 byprocessing the back-side of the piezoelectric thin film 120. Removingthe portion of the piezoelectric thin film 120 that was first formed onthe substrate can eliminate the lower crystallinity portion of thepiezoelectric thin film such that the remaining portion of thepiezoelectric thin film 120 has a higher crystallinity. For example, insome embodiments, a piezoelectric thin film of AlN or AlScN can beprocessed to remove about at least 500 Angstroms of material from theback-side of the film (the portion that was first formed on thesubstrate) so that the remaining portion has a crystallinity of lessthan about 1.0 degree at Full Width Half Maximum (FWHM) to about 10arcseconds at FWHM measured using X-ray diffraction (XRD). In someembodiments, the crystallinity of the piezoelectric thin film can be ina range between about 1.0 degree at FWHM to about 0.5 degrees at FWHMmeasured using XRD.

In some embodiments, the substrate 110 may optionally be heated to arelatively high sputtering temperature, such as about 350 degreesCentigrade to about 850 degrees Centigrade during formation of thepiezoelectric thin film 120. In some embodiments, the sputteringtemperature can be in a range between about 400 degrees Centigrade toabout 600 Degrees centigrade. In some embodiments according to theinvention, lower temperatures may also be used to sputter thepiezoelectric thin films 120 described herein onto the substrate.

In some embodiments, the piezoelectric thin film 120 can be formeddirectly on the substrate such that the piezoelectric thin film 120contacts the surface of the substrate. In some embodiments, a seed layercan be formed on the substrate 110 before forming the piezoelectric thinfilm 120 so that the seed layer is located between the substrate 110 andthe piezoelectric thin film 120. Accordingly, in some embodiments theseed layer is included in the first formed portion of the piezoelectricthin film 120, which may be removed from the back-side as describedherein. In some embodiments, the seed layer includes one or more GroupIII elements that are also included in the piezoelectric thin film 120.For example, the seed layer can be formed to include Al if thepiezoelectric thin film 120 comprises AlN or to include Al and Sc if thepiezoelectric thin film 120 includes AlScN. Other Group III elements andseed layer components can also be used. In some embodiments, the seedlayer can be formed using the same temperature used to form thepiezoelectric thin film.

In some embodiments, the seed layer can be formed at a temperature thatis less than the temperature used to form the piezoelectric thin film120. For example, the seed layer may be formed at a temperature lessthan 400 degrees Centigrade whereas the temperature can be increased tomore than 400 degrees Centigrade to about 600 Degrees centigrade whenforming the piezoelectric thin film 120. In some embodiments, the seedlayer can include Al and the piezoelectric thin film can be formed ofAlN. In some embodiments, the seed layer can include Al and Sc and thepiezoelectric thin film can be formed of AlScN. In some embodiments, thesputtering can be done with separate targets (for example a first targetof Al and a second target of Sc). It will be understood that theoperations described above can each be applied to the formation andprocessing of the piezoelectric thin film utilized in any of theembodiments described herein, including the piezoelectric thin filmsshown and described herein with reference to FIGS. 8-9A, 22-23, 39-40,and 52-53 .

FIG. 60 is a flowchart illustrating methods of forming a piezoelectricthin film on a substrate, which may be subsequently processed to exposethe back-side surface of the film and to remove the portion of the filmthat was first formed on the substrate as described in reference to, forexample, FIGS. 8-9A, 22-23, 39-40, and 52-53 in some embodimentsaccording to the invention. FIG. 61 is a schematic illustration of asputtering chamber that can be used to form the high crystallinitypiezoelectric thin films on the substrate 100 using a Group III targetmaterial (such as Al, Sc, or Al and Sc) in a plasma environmentincluding the capability to heat the substrate 100 to a relatively highsputtering temperature in some embodiments according to the invention.

According to FIGS. 60, 61, 62, and 63 the substrate (includingsubstrates 100, 1610, 3210, and 4710 shown in FIGS. 8-9A, 22-23, 39-40,52-53 , respectively) can be loaded into the sputtering process chamber6145 illustrated in FIG. 61 (block 6005). It will be understood that thesubstrate 100 may comprise Silicon, Sapphire, SiC, or other material. Insome embodiments, the substrate 100 may be pre-processed prior tosputtering. For example, the substrate 100 may be etched to remove anyunwanted oxides and/or may be heated to out-gas any materials from thesubstrate 100. Still further, these processes may be carried out in achamber that is coupled to the sputtering process chamber 6145 via acluster type configuration or carried out in a separate system.

The atmosphere in the sputtering process chamber 6145 may be stabilizedprior to the sputtering process (block 6010). It will be understood thatthe term “stabilize” means (in reference to the sputtering processchamber 6145) that the controllable parameters associated with thesputtering process described herein are brought to their initial valuesbefore conducting the subsequent sputtering operations. For example,controllable parameters associated with the sputtering process describedherein can include pressure in the chamber, temperature of thesubstrate, power levels applied to the cathode and anode, theconcentrations and amounts of the inert and process gases, the plasma,etc. as these parameters may drift during the sputtering process. Insome embodiments, the inert gas 6196 and the process gas 6197 gas areintroduced into the sputtering process chamber 6145 maintained at apressure of about 1 to 5 mTorr. In some embodiments, the inert gas 6196may be Argon and the process gas 6197 may be Nitrogen.

In some embodiments according to the invention, the piezoelectric thinfilm (including piezoelectric thin films 120, 1620, 3220, and 4720 shownin FIGS. 8-9A, 22-23, 39-40, 52-53 , respectively) is formed directly onthe substrate (as shown, for example, in FIG. 62 ) by sputtering atarget 6150 using the ionized inert gas 6196 to create a plasma 6170 asshown in FIG. 61 . It will be understood that the target can include anelement selected from Group III (such as Al or Sc), which can be used toform a nitride of the target material as the piezoelectric thin film 120on the substrate 100 using the Nitrogen process gas 6197 (block 6035).Accordingly, the piezoelectric thin film can be, for example, AlN,AlScN, AlCrN, HfMgAlN, or ZrMgAlN.

During the sputtering, a power level is provided at a cathode 6160coupled to the target 6150 which creates the plasma 6170 (due to theionization of the inert gas 6196) to eject the Group III element(s) fromthe target 6150 onto the substrate thereby forming the piezoelectricthin film 120 on the substrate. In some embodiments, the power levelprovided to the cathode 6160 can be changed during the sputtering. Instill further embodiments, a substrate bias 6190 may be applied to thesubstrate via an anode 6185 during the sputtering of the Group IIIelement(s) to adjust the strain within the piezoelectric thin film.

It will be further understood that in some embodiments according to theinvention, the target can be first and second separate targets that eachinclude an element selected from Group III (such as Al and Sc), whichcan be used to form a nitride of the target material as thepiezoelectric thin film 120 on the substrate 100 using the Nitrogenprocess gas 6197. Accordingly, the piezoelectric thin film can be formedto be, for example AlScN, in the case of the first and second separatetargets including respective Group III elements.

It will be further understood that in some embodiments according to theinvention, the target can be a composite target that includes the firstand second target materials selected from Group III (such as Al and Sc),which can be used to form a nitride of the target material as thepiezoelectric thin film on the substrate using the Nitrogen process gas6197. Accordingly, the piezoelectric thin film can be, for exampleAlScN, in the case of the target including two Group III elements. Itwill be understood that more than two Group III elements may be used aseither separate targets or as a single composite target. Further anycombination of targets and Group III elements may be used.

In some embodiments according to the invention, an optional seed layer6101 can be formed directly on the substrate to form a nucleation layerprior to formation of the piezoelectric thin film, as shown in FIG. 63(block 6020). In some embodiments, the seed layer 6101 is formed toinclude the same Group III element(s) included in the piezoelectric thinfilm. For example, if the piezoelectric thin film includes AlN, the seedlayer 6101 can be formed using Al. In some embodiments, when thepiezoelectric thin film includes AlScN, the seed layer 6101 can beformed using Al and Sc. During the sputtering of the seed layer 6101, apower level can be provided at the cathode 6160 coupled to the target6150 which creates the plasma 6170 (due to the ionization of the inertgas 6196) to eject the Group III element(s) from the target 6150 ontothe substrate thereby forming the seed layer 6101 on the substrate. Insome embodiments, the power level provided to the cathode 6160 can bechanged during the sputtering of the seed layer 6101. In still furtherembodiments, the power level at the cathode 6160 may be changed duringthe sputtering of the Group III element(s) onto the substrate to adjustthe strain within the seed layer 6101. After formation of the optionalseed layer 6101, the sputtering process chamber 6145 can be stabilizedby adjusting the pressure and flows of the inert gas 6196 and theprocess gas 6197 (block 6025) before sputtering the piezoelectric thinfilm onto the seed layer 6101.

In some embodiments, the piezoelectric thin film is subjected to partialremoval (block 6035) from the back-side so that the portion of thepiezoelectric thin film that is first formed on the substrate is removedas described, for example, in reference to FIGS. 8-9, 22-23, 39-40, and52-53 herein. Accordingly, a high crystallinity piezoelectric thin filmmay be formed on the substrate by sputtering a Group III target material(such as Al, Sc, or Al and Sc, and other materials) in a plasmaenvironment and subsequently removing the first formed portion of thepiezoelectric thin film by processing the substrate to expose theback-side of the piezoelectric thin film (block 6037) (the portion thatwas first formed on the substrate) and to further remove the portion ofthe piezoelectric thin film 120 that was first formed on the substrate(block 6039) to eliminate the lower crystallinity portion of thepiezoelectric thin film so that the remaining portion of thepiezoelectric thin film has a higher crystallinity. For example, in someembodiments, a piezoelectric thin film of AlN or AlScN can be processedto remove about at least 500 Angstroms of material from the back-side ofthe film (the portion that was first formed on the substrate) so thatthe remaining portion has a crystallinity of less than about 1.0 degreeat Full Width Half Maximum (FWHM) to about 10 arcseconds at FWHMmeasured using X-ray diffraction (XRD). In some embodiments, thecrystallinity of the piezoelectric thin film can be in a range betweenabout 1.0 degree at FWHM to about 0.5 degrees at FWHM measured usingXRD.

It will also be understood that in some embodiments, the piezoelectricthin films can be formed via sputtering or other methods, such as CVD.For example, the piezoelectric thin films subject to partial removalfrom the back-side as described herein can be formed using the hightemperature sputtering process as illustrated by FIG. 64 , a lowertemperature sputtering process, or a CVD process. It will be furtherunderstood that these processes can be applied to all of the embodimentsdescribed herein, such as those related FIGS. 1-15, 16-31, 32-46, and47-59 (block 6040).

FIG. 65 is a graph illustrating impedance of an acoustic resonator as afunction of frequency, including a piezoelectric thin film formed byremoving about a 500 Angstrom portion from the surface that was firstformed on the substrate in some embodiments according to the inventioncompared to a conventionally formed piezoelectric thin film.

FIG. 66 is a graph illustrating a Q factor of an acoustic resonator as afunction of frequency, including a piezoelectric thin film formed byremoving about a 500 Angstrom portion from the surface that was firstformed on the substrate in some embodiments according to the inventioncompared to a conventionally formed piezoelectric thin film.

FIG. 64 is a flowchart illustrating methods of forming a piezoelectricthin film on a substrate that is heated to the sputtering temperature toprovide the piezoelectric thin film, which may be subsequently processedto expose the back-side surface of the film and to remove the portion ofthe film that was first formed on the substrate as described inreference to, for example, FIGS. 8-9A, 22-23, 39-40, 52-53 in someembodiments according to the invention. FIG. 61 is a schematicillustration of a sputtering chamber that can be used to form the highcrystallinity piezoelectric thin films on the substrate using a GroupIII target material (such as Al, Sc, or Al and Sc) in a plasmaenvironment where the substrate is heated to a relatively highsputtering temperature in some embodiments according to the invention.

According to FIG. 64 , the substrate (including substrates 100, 1610,3210, and 4710 shown in FIGS. 8-9A, 22-23, 39-40, 52-53 , respectively)can be loaded into the sputtering process chamber 6145 illustrated inFIG. 61 (block 6405). It will be understood that the substrate maycomprise Silicon, Sapphire, SiC, or other material. In some embodiments,the substrate may be pre-processed prior to sputtering. For example, thesubstrate may be etched to remove any unwanted oxides and/or may beheated to out-gas any materials from the substrate. Still further, theseprocesses may be carried out in a chamber that is coupled to thesputtering process chamber 6145 via a cluster type configuration orcarried out in a separate system.

The atmosphere in the sputtering process chamber 6145 may be stabilizedprior to the sputtering process (block 6410). It will be understood thatthe term “stabilize” means (in reference to the sputtering processchamber 6145) that the controllable parameters associated with thesputtering process described herein are brought to their initial valuesbefore conducting the subsequent sputtering operations. For example,controllable parameters associated with the sputtering process describedherein can include pressure in the chamber, temperature of thesubstrate, power levels applied to the cathode and anode, theconcentrations and amounts of the inert and process gases, the plasma,etc. as these parameters may drift during the sputtering process. Insome embodiments, the inert gas 6196 and the process gas 6197 gas areintroduced into the sputtering process chamber 6145 maintained at apressure of about 1 to 5 mTorr. In some embodiments, the inert gas 6196may be Argon and the process gas 6197 may be Nitrogen.

In some embodiments, the substrate is heated to a sputtering temperaturein a range between about 350 degrees Centigrade to about 850 degreesCentigrade using the heater 6180 (block 6415). In some embodiments, thesubstrate 100 is heated to a sputtering temperature in a range betweenabout 400 degrees Centigrade to about 600 degrees Centigrade. In someembodiments, the sputtering temperature may be changed during thesputtering process to improve the level of crystallinity of thepiezoelectric layer. It will be understood that the process chamber 6145may also include a feedback mechanism to ensure that the temperature ofthe substrate is maintained at the set point that is indicated to be thesputtering temperature as described herein.

In some embodiments according to the invention, the piezoelectric thinfilm (including piezoelectric thin films 120, 1620, 3220, and 4720 shownin FIGS. 8-9A, 22-23, 39-40, 52-53 , respectively) is formed directly onthe substrate at a temperature in the sputtering temperature range bysputtering a target 6150 using the ionized inert gas 6196 to create aplasma 6170 as shown in FIG. 61 (block 6430). It will be understood thatthe target can include an element selected from Group III (such as Al orSc), which can be used to form a nitride of the target material as thepiezoelectric thin film on the substrate using the Nitrogen process gas6197. Accordingly, the piezoelectric thin film can be, for example, AlN,AlScN, AlCrN, HfMgAlN, or ZrMgAlN. Other materials may also be used.

During the sputtering, a power level is provided at a cathode 6160coupled to the target 6150 which creates the plasma 6170 (due to theionization of the inert gas 6196) to eject the Group III element(s) fromthe target 6150 onto the substrate thereby forming the piezoelectricthin film on the substrate. In some embodiments, the power levelprovided to the cathode 6160 can be changed during the sputtering. Instill further embodiments, a substrate bias 6190 may be applied to thesubstrate via an anode 6185 during the sputtering of the Group IIIelement(s) to adjust the strain within the piezoelectric thin film.

It will be further understood that in some embodiments according to theinvention, the target can be first and second separate targets that eachinclude an element selected from Group III (such as Al and Sc), whichcan be used to form a nitride of the target material as thepiezoelectric thin film on the substrate using the Nitrogen process gas6197. Accordingly, the piezoelectric thin film can be formed to be, forexample AlScN, in the case of the first and second separate targetsincluding respective Group III elements.

It will be further understood that in some embodiments according to theinvention, the target can be a composite target that includes the firstand second target materials selected from Group III (such as Al and Sc),which can be used to form a nitride of the target material as thepiezoelectric thin film on the substrate using the Nitrogen process gas6197 Accordingly, the piezoelectric thin film can be, for example AlScN,in the case of the target including two Group III elements. It will beunderstood that more than two Group III elements may be used as eitherseparate targets or as a single composite target. Further anycombination of targets and Group III elements may be used.

In some embodiments according to the invention, the optional seed layer6101 can be formed directly on the substrate at a temperature in thesputtering temperature range so as to form a nucleation layer prior toformation of the piezoelectric thin film, as shown in FIG. 62 (block6420). In some embodiments, the seed layer 6101 is formed to include thesame Group III element(s) included in the piezoelectric thin film. Forexample, if the piezoelectric thin film includes AlN, the seed layer6101 can be formed using Al. In some embodiments, when the piezoelectricthin film includes AlScN, the seed layer 6101 can be formed using Al andSc. During the sputtering of the seed layer 6101, a power level can beprovided at the cathode 6160 coupled to the target 6150 which createsthe plasma 6170 (due to the ionization of the inert gas 6196) to ejectthe Group III element(s) from the target 6150 onto the substrate therebyforming the seed layer 6101 on the substrate. In some embodiments, thepower level provided to the cathode 6160 can be changed during thesputtering of the seed layer 6101. In still further embodiments, thepower level at the cathode 6160 may be changed during the sputtering ofthe Group III element(s) onto the substrate to adjust the strain withinthe seed layer 6101.

As appreciated by the present inventors, the seed layer 6101 may beformed at a first temperature within sputtering temperature rangewhereas the piezoelectric thin film can be formed at a temperature thatis also within the sputtering temperature range but is greater than thetemperature used to sputter the seed layer 6101 onto the substrate 100.The lower sputtering temperature used to form the seed layer 6101(compared to the temperature used to form the piezoelectric thin film)can provide still greater crystallinity in the piezoelectric thin filmsputtered onto the seed layer 6101. After formation of the seed layer6101, the sputtering process chamber 6145 can be stabilized by adjustingthe pressure and flows of the inert gas 6196 and the process gas 6197(block 6430).

In some embodiments, the piezoelectric thin film is subjected to partialremoval from the back-side so that the portion of the piezoelectric thinfilm that is first formed on the substrate is removed as described, forexample, in reference to FIGS. 8-9, 22-23, 39-40, and 52-53 herein.Accordingly, a high crystallinity piezoelectric thin film may be formedon the substrate heated to the sputtering temperature by sputtering aGroup III target material (such as Al, Sc, or Al and Sc, and othermaterials) in a plasma environment and subsequently removing the firstformed portion of the piezoelectric thin film by processing thesubstrate (block 6437) to expose the back-side of the piezoelectric thinfilm (the portion that was first formed on the substrate) and to furtherremove a portion of the piezoelectric thin film that was first formed onthe substrate (block 6439). Removing the portion of the piezoelectricthin film that was first formed on the substrate can eliminate the lowercrystallinity portion of the piezoelectric thin film such that theremaining portion of the piezoelectric thin film has a highercrystallinity. For example, in some embodiments, a piezoelectric thinfilm of AlN or AlScN can be processed to remove about at least 500Angstroms of material from the back-side of the film (the portion thatwas first formed on the substrate) so that the remaining portion has acrystallinity of less than about 1.0 degree at Full Width Half Maximum(FWHM) to about 10 arcseconds at FWHM measured using X-ray diffraction(XRD). In some embodiments, the crystallinity of the piezoelectric thinfilm can be in a range between about 1.0 degree at FWHM to about 0.5degrees at FWHM measured using XRD.

It will also be understood that in some embodiments, the piezoelectricthin films can be formed via sputtering or other methods, such as CVD.For example, the piezoelectric thin films subject to partial removalfrom the back-side as described herein can be formed using the hightemperature sputtering process as illustrated by FIG. 64 , a lowertemperature sputtering process, or a CVD process. It will be furtherunderstood that these processes can be applied to all of the embodimentsdescribed herein, such as those related FIGS. 1-15, 16-31, 32-46, and47-59 to form an acoustic resonator (block 6440).

It will also be understood that in some embodiments, the piezoelectricthin films can be formed via sputtering or other methods, such as CVD.For example, the piezoelectric thin films subject to partial removalfrom the back-side as described herein can be formed using the hightemperature sputtering process as illustrated by FIG. 64 , a lowertemperature sputtering process, or a CVD process. It will be furtherunderstood that these processes can be applied to all of the embodimentsdescribed herein, such as those related FIGS. 16-31, 32-46, and 47-59 .

FIG. 3 can represent a method step of forming a top side metallizationor top resonator metal electrode 130. In a specific example, the topsidemetal electrode 130 can include a molybdenum, aluminum, ruthenium, ortitanium material, or the like and combinations thereof. This layer canbe deposited and patterned on top of the piezoelectric layer by alift-off process, a wet etching process, a dry etching process, a metalprinting process, a metal laminating process, or the like. The lift-offprocess can include a sequential process of lithographic patterning,metal deposition, and lift-off steps to produce the topside metal layer.The wet/dry etching processes can include sequential processes of metaldeposition, lithographic patterning, metal deposition, and metal etchingsteps to produce the topside metal layer. Those of ordinary skill in theart will recognize other variations, modifications, and alternatives.

FIG. 4A is a simplified diagram illustrating a step for a method ofmanufacture for an acoustic resonator device 401 according to an exampleof the present invention. This figure can represent a method step offorming one or more topside micro-trenches 121 within a portion of thepiezoelectric layer 120. This topside micro-trench 121 can serve as themain interconnect junction between the top and bottom sides of theacoustic membrane, which will be developed in later method steps. In anexample, the topside micro-trench 121 is extends all the way through thepiezoelectric layer 120 and stops in the seed substrate 110. Thistopside micro-trench 121 can be formed through a dry etching process, alaser drilling process, or the like. FIGS. 4B and 4C describe theseoptions in more detail.

FIGS. 4B and 4C are simplified diagrams illustrating alternative methodsfor conducting the method step as described in FIG. 4A. As shown, FIG.4B represents a method step of using a laser drill, which can quicklyand accurately form the topside micro-trench 121 in the piezoelectriclayer 120. In an example, the laser drill can be used to form nominal 50um holes, or holes between 10 um and 500 um in diameter, through thepiezoelectric layer 120 and stop in the seed substrate 110 below theinterface between layers 120 and 110. A protective layer 122 can beformed overlying the piezoelectric layer 120 and the topside metalelectrode 130. This protective layer 122 can serve to protect the devicefrom laser debris and to provide a mask for the etching of the topsidemicro-via 121. In a specific example, the laser drill can be an 11 Whigh power diode-pumped UV laser, or the like. This mask 122 can besubsequently removed before proceeding to other steps. The mask may alsobe omitted from the laser drilling process, and air flow can be used toremove laser debris.

FIG. 4C can represent a method step of using a dry etching process toform the topside micro-trench 121 in the piezoelectric layer 120. Asshown, a lithographic masking layer 123 can be forming overlying thepiezoelectric layer 120 and the topside metal electrode 130. The topsidemicro-trench 121 can be formed by exposure to plasma, or the like.

FIGS. 4D and 4E are simplified diagrams illustrating an alternativemethod for conducting the method step as described in FIG. 4A. Thesefigures can represent the method step of manufacturing multiple acousticresonator devices simultaneously. In FIG. 4D, two devices are shown onDie #1 and Die #2, respectively. FIG. 4E shows the process of forming amicro-via 121 on each of these dies while also etching a scribe line 124or dicing line. In an example, the etching of the scribe line 124singulates and relieves stress in the piezoelectric single crystal layer120.

FIGS. 5 to 8 are simplified diagrams illustrating steps for a method ofmanufacture for an acoustic resonator device according to an example ofthe present invention. FIG. 5 can represent the method step of formingone or more bond pads 140 and forming a topside metal 141 electricallycoupled to at least one of the bond pads 140. The topside metal 141 caninclude a topside metal plug 146 formed within the topside micro-trench121. In a specific example, the topside metal plug 146 fills the topsidemicro-trench 121 to form a topside portion of a micro-via.

In an example, the bond pads 140 and the topside metal 141 can include agold material or other interconnect metal material depending upon theapplication of the device. These metal materials can be formed by alift-off process, a wet etching process, a dry etching process, ascreen-printing process, an electroplating process, a metal printingprocess, or the like. In a specific example, the deposited metalmaterials can also serve as bond pads for a cap structure, which will bedescribed below.

FIG. 6 can represent a method step for preparing the acoustic resonatordevice for bonding, which can be a hermetic bonding. As shown, a top capstructure is positioned above the partially processed acoustic resonatordevice as described in the previous figures. The top cap structure canbe formed using an interposer substrate 119 in two configurations: fullyprocessed interposer version 601 (through glass via) and partiallyprocessed interposer version 602 (blind via version). In the 601version, the interposer substrate 119 includes through-via structures151 that extend through the interposer substrate 119 and areelectrically coupled to bottom bond pads 142 and top bond pads 143. Inthe 602 version, the interposer substrate 119 includes blind viastructures 152 that only extend through a portion of the interposersubstrate 119 from the bottom side. These blind via structures 152 arealso electrically coupled to bottom bond pads 142. In a specificexample, the interposer substrate can include a silicon, glass,smart-glass, or other like material.

FIG. 7 can represent a method step of bonding the top cap structure tothe partially processed acoustic resonator device. As shown, theinterposer substrate 119 is bonded to the piezoelectric layer by thebond pads (140, 142) and the topside metal 141, which are now denoted asbond pad 144 and topside metal 145. This bonding process can be doneusing a compression bond method or the like. FIG. 8 can representthinning the seed substrate 110, which may be denoted as thinned seedsubstrate 111. This substrate thinning process can include grinding andetching processes or the like. In a specific example, this process caninclude a wafer backgrinding process followed by stress removal, whichcan involve dry etching, CMP polishing, or annealing processes.

It will be understood that, in some embodiments, the substrate may beremoved entirely to expose the surface of the piezoelectric thin film120 and to remove a first formed portion of the piezoelectric thin film120 (or the piezoelectric layer 6120 or 6101 shown in FIGS. 62-63 ). Forexample, in some embodiments, the substrate thinning process may beperformed to expose the surface of the piezoelectric thin film 120 andfurther to remove about at least about 500 Angstroms of material fromthe exposed surface of the piezoelectric thin film. As appreciated bythe present inventors, the removal of a portion of the exposedpiezoelectric layer can remove a relatively low quality crystallinityportion of the piezoelectric thin film, so that the remaining portion ofthe piezoelectric thin film is of relatively higher qualitycrystallinity, to have a crystallinity of less than about 1.0 degree atFull Width Half Maximum (FWHM) to about 10 arcseconds at FWHM measuredusing X-ray diffraction (XRD). In some embodiments, the crystallinity ofthe piezoelectric thin film can be in a range between about 1.0 degreeat FWHM to about 0.5 degrees at FWHM measured using XRD.

It will be further understood that the piezoelectric thin film accordingto some embodiments, such as piezoelectric thin films 120, 1620, 3220,and 4720 shown in FIGS. 8-9A, 22-23, 39-40, 52-53 , respectively) can beany Group III material that is doped with one or more elements that areselected to change the crystal structure of the Group III material tomodify the piezoelectric properties on the piezoelectric thin film. Forexample, in some embodiments the piezoelectric thin film can be AlScNand the exposed surface can be processed to remove about the first 500Angstroms of the AlScN. It will be further understood that the amount ofpiezoelectric thin film 120 that is removed can be selected so as toimprove the overall performance (such as the coupling coefficient) ofthe piezoelectric thin film used in the acoustic resonator device. Theselected amount may further be based on the materials used to form thepiezoelectric thin film; the process used to form the piezoelectric thinfilm 120.

FIG. 9A is a simplified diagram illustrating a step for a method ofmanufacture for an acoustic resonator device 901 according to an exampleof the present invention. FIG. 9A can represent a method step forforming backside trenches 113 and 114 to allow access to thepiezoelectric layer 120 (or the piezoelectric layer 6120 or 6101 shownin FIGS. 62-63 ) from the backside of the thinned seed substrate 111. Insome embodiments, it will be understood that the substrate thinningprocess described above in reference to FIG. 8 may be performed incombination with the process shown in FIG. 9A where the exposed portionsof the surface of the piezoelectric layer are further processed toremove the portion of the exposed piezoelectric layer. For example, insome embodiments, the removal of the first formed portion of the exposedpiezoelectric layer can be performed using the thinned substrate 112 asa mask to further to remove the lowest most portions of thepiezoelectric thin film that are exposed by the thinned substrate 112.It will be understood that in some embodiments according to theinvention, the techniques described above in reference to FIG. 8 to canalso be used in accordance with FIG. 9A. It will be further understoodthat the processes described above regarding the removal of a portion ofthe piezoelectric thin film that is first formed on the substrate can beapplied to the other embodiments described herein, such as those relatedFIGS. 16-31, 32-46, and 47-59 . For example, the removal of a firstformed portion of the piezoelectric thin film formed using a variety ofprocesses can be applied to the structures and processes described inreference FIGS. 24, 41, and 53 .

In an example, the first backside trench 113 can be formed within thethinned seed substrate 111 and underlying the topside metal electrode130. The second backside trench 114 can be formed within the thinnedseed substrate 111 and underlying the topside micro-trench 121 andtopside metal plug 146. This substrate is now denoted thinned substrate112. In a specific example, these trenches 113 and 114 can be formedusing deep reactive ion etching (DRIE) processes, Bosch processes, orthe like. The size, shape, and number of the trenches may vary with thedesign of the acoustic resonator device. In various examples, the firstbackside trench may be formed with a trench shape similar to a shape ofthe topside metal electrode or a shape of the backside metal electrode.The first backside trench may also be formed with a trench shape that isdifferent from both a shape of the topside metal electrode and thebackside metal electrode.

FIGS. 9B and 9C are simplified diagrams illustrating an alternativemethod for conducting the method step as described in FIG. 9A. LikeFIGS. 4D and 4E, these figures can represent the method step ofmanufacturing multiple acoustic resonator devices simultaneously. InFIG. 9B, two devices with cap structures are shown on Die #1 and Die #2,respectively. FIG. 9C shows the process of forming backside trenches(113, 114) on each of these dies while also etching a scribe line 115 ordicing line. In an example, the etching of the scribe line 115 providesan optional way to singulate the backside wafer 112.

FIG. 10 is a simplified diagram illustrating a step for a method ofmanufacture for an acoustic resonator device 1000 according to anexample of the present invention. This figure can represent a methodstep of forming a backside metal electrode 131 and a backside metal plug147 within the backside trenches of the thinned seed substrate 112. Inan example, the backside metal electrode 131 can be formed underlyingone or more portions of the thinned substrate 112, within the firstbackside trench 113, and underlying the topside metal electrode 130.This process completes the resonator structure within the acousticresonator device. The backside metal plug 147 can be formed underlyingone or more portions of the thinned substrate 112, within the secondbackside trench 114, and underlying the topside micro-trench 121. Thebackside metal plug 147 can be electrically coupled to the topside metalplug 146 and the backside metal electrode 131. In a specific example,the backside metal electrode 130 can include a molybdenum, aluminum,ruthenium, or titanium material, or the like and combinations thereof.The backside metal plug can include a gold material, low resistivityinterconnect metals, electrode metals, or the like. These layers can bedeposited using the deposition methods described previously.

FIGS. 11A and 11B are simplified diagrams illustrating alternative stepsfor a method of manufacture for an acoustic resonator device accordingto an example of the present invention. These figures show methods ofbonding a backside cap structure underlying the thinned seed substrate112. In FIG. 11A, the backside cap structure is a dry film cap 161,which can include a permanent photo-imageable dry film such as a soldermask, polyimide, or the like. Bonding this cap structure can becost-effective and reliable, but may not produce a hermetic seal. InFIG. 11B, the backside cap structure is a substrate 162, which caninclude a silicon, glass, or other like material. Bonding this substratecan provide a hermetic seal, but may cost more and require additionalprocesses. Depending upon application, either of these backside capstructures can be bonded underlying the first and second backside vias.

FIGS. 12A to 12E are simplified diagrams illustrating steps for a methodof manufacture for an acoustic resonator device according to an exampleof the present invention. More specifically, these figures describeadditional steps for processing the blind via interposer “602” versionof the top cap structure. FIG. 12A shows an acoustic resonator device1201 with blind vias 152 in the top cap structure. In FIG. 12B, theinterposer substrate 119 is thinned, which forms a thinned interposersubstrate 118, to expose the blind vias 152. This thinning process canbe a combination of a grinding process and etching process as describedfor the thinning of the seed substrate. In FIG. 12C, a redistributionlayer (RDL) process and metallization process can be applied to createtop cap bond pads 160 that are formed overlying the blind vias 152 andare electrically coupled to the blind vias 152. As shown in FIG. 12D, aball grid array (BGA) process can be applied to form solder balls 170overlying and electrically coupled to the top cap bond pads 160. Thisprocess leaves the acoustic resonator device ready for wire bonding 171,as shown in FIG. 12E.

FIG. 13 is a simplified diagram illustrating a step for a method ofmanufacture for an acoustic resonator device according to an example ofthe present invention. As shown, device 1300 includes two fullyprocessed acoustic resonator devices that are ready to singulation tocreate separate devices. In an example, the die singulation process canbe done using a wafer dicing saw process, a laser cut singulationprocess, or other processes and combinations thereof.

FIGS. 14A to 14G are simplified diagrams illustrating steps for a methodof manufacture for an acoustic resonator device according to an exampleof the present invention. This method illustrates the process forfabricating an acoustic resonator device similar to that shown in FIG.1B. The method for this example of an acoustic resonator can go throughsimilar steps as described in FIGS. 1-5 . FIG. 14A shows where thismethod differs from that described previously. Here, the top capstructure substrate 119 and only includes one layer of metallizationwith one or more bottom bond pads 142. Compared to FIG. 6 , there are novia structures in the top cap structure because the interconnectionswill be formed on the bottom side of the acoustic resonator device.

FIGS. 14B to 14F depict method steps similar to those described in thefirst process flow. FIG. 14B can represent a method step of bonding thetop cap structure to the piezoelectric layer 120 through the bond pads(140, 142) and the topside metal 141, now denoted as bond pads 144 andtopside metal 145 with topside metal plug 146. FIG. 14C can represent amethod step of thinning the seed substrate 110, which forms a thinnedseed substrate 111, similar to that described in FIG. 8 . FIG. 14D canrepresent a method step of forming first and second backside trenches,similar to that described in FIG. 9A. FIG. 14E can represent a methodstep of forming a backside metal electrode 131 and a backside metal plug147, similar to that described in FIG. 10 . FIG. 14F can represent amethod step of bonding a backside cap structure 162, similar to thatdescribed in FIGS. 11A and 11B.

FIG. 14G shows another step that differs from the previously describedprocess flow. Here, the backside bond pads 171, 172, and 173 are formedwithin the backside cap structure 162. In an example, these backsidebond pads 171-173 can be formed through a masking, etching, and metaldeposition processes similar to those used to form the other metalmaterials. A BGA process can be applied to form solder balls 170 incontact with these backside bond pads 171-173, which prepares theacoustic resonator device 1407 for wire bonding.

FIGS. 15A to 15E are simplified diagrams illustrating steps for a methodof manufacture for an acoustic resonator device according to an exampleof the present invention. This method illustrates the process forfabricating an acoustic resonator device similar to that shown in FIG.1B. The method for this example can go through similar steps asdescribed in FIG. 1-5 . FIG. 15A shows where this method differs fromthat described previously. A temporary carrier 218 with a layer oftemporary adhesive 217 is attached to the substrate. In a specificexample, the temporary carrier 218 can include a glass wafer, a siliconwafer, or other wafer and the like.

FIGS. 15B to 15F depict method steps similar to those described in thefirst process flow. FIG. 15B can represent a method step of thinning theseed substrate 110, which forms a thinned substrate 111, similar to thatdescribed in FIG. 8 . In a specific example, the thinning of the seedsubstrate 110 can include a back side grinding process followed by astress removal process. The stress removal process can include a dryetch, a Chemical Mechanical Planarization (CMP), and annealingprocesses.

FIG. 15C can represent a method step of forming a shared backside trench113, similar to the techniques described in FIG. 9A. The main differenceis that the shared backside trench is configured underlying both topsidemetal electrode 130, topside micro-trench 121, and topside metal plug146. In an example, the shared backside trench 113 is a backsideresonator cavity that can vary in size, shape (all possible geometricshapes), and side wall profile (tapered convex, tapered concave, orright angle). In a specific example, the forming of the shared backsidetrench 113 can include a litho-etch process, which can include aback-to-front alignment and dry etch of the backside substrate 111. Thepiezoelectric layer 120 can serve as an etch stop layer for the formingof the shared backside trench 113.

FIG. 15D can represent a method step of forming a backside metalelectrode 131 and a backside metal 147, similar to that described inFIG. 10 . In an example, the forming of the backside metal electrode 131can include a deposition and patterning of metal materials within theshared backside trench 113. Here, the backside metal 131 serves as anelectrode and the backside plug/connect metal 147 within the micro-via121. The thickness, shape, and type of metal can vary as a function ofthe resonator/filter design. As an example, the backside electrode 131and via plug metal 147 can be different metals. In a specific example,these backside metals 131, 147 can either be deposited and patterned onthe surface of the piezoelectric layer 120 or rerouted to the backsideof the substrate 112. In an example, the backside metal electrode may bepatterned such that it is configured within the boundaries of the sharedbackside trench such that the backside metal electrode does not come incontact with one or more side-walls of the seed substrate created duringthe forming of the shared backside trench.

FIG. 15E can represent a method step of bonding a backside cap structure162, similar to that described in FIGS. 11A and 11B, following ade-bonding of the temporary carrier 218 and cleaning of the topside ofthe device to remove the temporary adhesive 217. Those of ordinary skillin the art will recognize other variations, modifications, andalternatives of the methods steps described previously.

As used herein, the term “substrate” can mean the bulk substrate or caninclude overlying growth structures such as an aluminum, gallium, orternary compound of aluminum and gallium and nitrogen containingepitaxial region, or functional regions, combinations, and the like.

One or more benefits are achieved over pre-existing techniques using theinvention. In particular, the present device can be manufactured in arelatively simple and cost effective manner while using conventionalmaterials and/or methods according to one of ordinary skill in the art.Using the present method, one can create a reliable single crystal basedacoustic resonator using multiple ways of three-dimensional stackingthrough a wafer level process. Such filters or resonators can beimplemented in an RF filter device, an RF filter system, or the like.Depending upon the embodiment, one or more of these benefits may beachieved. Of course, there can be other variations, modifications, andalternatives.

With 4G LTE and 5G growing more popular by the day, wireless datacommunication demands high performance RF filters with frequenciesaround 5 GHz and higher. Bulk acoustic wave resonators (BAWR), widelyused in such filters operating at frequencies around 3 GHz and lower,are leading candidates for meeting such demands. Current bulk acousticwave resonators use polycrystalline piezoelectric AlN thin films whereeach grain's c-axis is aligned perpendicular to the film's surface toallow high piezoelectric performance whereas the grains' a- or b-axisare randomly distributed. This peculiar grain distribution works wellwhen the piezoelectric film's thickness is around 1 um and above, whichis the perfect thickness for bulk acoustic wave (BAW) filters operatingat frequencies ranging from 1 to 3 GHz. However, the quality of thepolycrystalline piezoelectric films degrades quickly as the thicknessesdecrease below around 0.5 um, which is required for resonators andfilters operating at frequencies around 5 GHz and above.

Single crystalline or epitaxial piezoelectric thin films grown oncompatible crystalline substrates exhibit good crystalline quality andhigh piezoelectric performance even down to very thin thicknesses, e.g.,0.4 um. The present invention provides manufacturing processes andstructures for high quality bulk acoustic wave resonators with singlecrystalline or epitaxial piezoelectric thin films for high frequency BAWfilter applications.

BAWRs require a piezoelectric material, e.g., AlN, in crystalline form,i.e., polycrystalline or single crystalline. The quality of the filmheavy depends on the chemical, crystalline, or topographical quality ofthe layer on which the film is grown. In conventional BAWR processes(including film bulk acoustic resonator (FBAR) or solidly mountedresonator (SMR) geometry), the piezoelectric film is grown on apatterned bottom electrode, which is usually made of molybdenum (Mo),tungsten (W), or ruthenium (Ru). The surface geometry of the patternedbottom electrode significantly influences the crystalline orientationand crystalline quality of the piezoelectric film, requiring complicatedmodification of the structure.

Thus, the present invention uses single crystalline piezoelectric filmsand thin film transfer processes to produce a BAWR with enhancedultimate quality factor and electro-mechanical coupling for RF filters.Such methods and structures facilitate methods of manufacturing andstructures for RF filters using single crystalline or epitaxialpiezoelectric films to meet the growing demands of contemporary datacommunication.

In an example, the present invention provides transfer structures andprocesses for acoustic resonator devices, which provides a flat,high-quality, single-crystal piezoelectric film for superior acousticwave control and high Q in high frequency. As described above,polycrystalline piezoelectric layers limit Q in high frequency. Also,growing epitaxial piezoelectric layers on patterned electrodes affectsthe crystalline orientation of the piezoelectric layer, which limits theability to have tight boundary control of the resulting resonators.Embodiments of the present invention, as further described below, canovercome these limitations and exhibit improved performance andcost-efficiency.

FIGS. 16A-16C through FIGS. 31A-31C illustrate a method of fabricationfor an acoustic resonator device using a transfer structure with asacrificial layer. In these figure series described below, the “A”figures show simplified diagrams illustrating top cross-sectional viewsof single crystal resonator devices according to various embodiments ofthe present invention. The “B” figures show simplified diagramsillustrating lengthwise cross-sectional views of the same devices in the“A” figures. Similarly, the “C” figures show simplified diagramsillustrating widthwise cross-sectional views of the same devices in the“A” figures. In some cases, certain features are omitted to highlightother features and the relationships between such features. Those ofordinary skill in the art will recognize variations, modifications, andalternatives to the examples shown in these figure series.

FIGS. 16A-16C are simplified diagrams illustrating variouscross-sectional views of a single crystal acoustic resonator device andof method steps for a transfer process using a sacrificial layer forsingle crystal acoustic resonator devices according to an example of thepresent invention. As shown, these figures illustrate the method step offorming a piezoelectric thin film 1620 overlying a growth substrate1610. In an example, the growth substrate 1610 can include silicon (S),silicon carbide (SiC), Sapphire, or other like materials. Thepiezoelectric film 1620 can be a film including a Group III nitride,such as aluminum nitride (AlN), gallium nitride (GaN), or other likematerials. Additionally, this piezoelectric substrate can be subjectedto a thickness trim. The piezoelectric thin film 1620 (with or without aseed layer) can be formed as described above in reference to FIGS. 60-64in some embodiments.

FIGS. 17A-17C are simplified diagrams illustrating variouscross-sectional views of a single crystal acoustic resonator device andof method steps for a transfer process using a sacrificial layer forsingle crystal acoustic resonator devices according to an example of thepresent invention. As shown, these figures illustrate the method step offorming a first electrode 1710 overlying the surface region of thepiezoelectric thin film 1620. In an example, the first electrode 1710can include molybdenum (Mo), ruthenium (Ru), tungsten (W), or other likematerials. In a specific example, the first electrode 1710 can besubjected to a dry etch with a slope. As an example, the slope can beabout 60 degrees.

FIGS. 18A-18C are simplified diagrams illustrating variouscross-sectional views of a single crystal acoustic resonator device andof method steps for a transfer process using a sacrificial layer forsingle crystal acoustic resonator devices according to an example of thepresent invention. As shown, these figures illustrate the method step offorming a first passivation layer 1810 overlying the first electrode1710 and the piezoelectric thin film 1620. In an example, the firstpassivation layer 1810 can include silicon nitride (SiN), silicon oxide(SiOx), or other like materials. In a specific example, the firstpassivation layer 1810 can have a thickness ranging from about 50 nm toabout 100 nm.

FIGS. 19A-19C are simplified diagrams illustrating variouscross-sectional views of a single crystal acoustic resonator device andof method steps for a transfer process using a sacrificial layer forsingle crystal acoustic resonator devices according to an example of thepresent invention. As shown, these figures illustrate the method step offorming a sacrificial layer 1910 overlying a portion of the firstelectrode 1810 and a portion of the piezoelectric film 1620. In anexample, the sacrificial layer 1910 can include polycrystalline silicon(poly-Si), amorphous silicon (a-Si), or other like materials. In aspecific example, this sacrificial layer 1910 can be subjected to a dryetch with a slope and be deposited with a thickness of about 1 um.Further, phosphorous doped SiO.sub.2 (PSG) can be used as thesacrificial layer with different combinations of support layer (e.g.,SiNx).

FIGS. 20A-20C are simplified diagrams illustrating variouscross-sectional views of a single crystal acoustic resonator device andof method steps for a transfer process using a sacrificial layer forsingle crystal acoustic resonator devices according to an example of thepresent invention. As shown, these figures illustrate the method step offorming a support layer 2010 overlying the sacrificial layer 1910, thefirst electrode 1710, and the piezoelectric thin film 1620. In anexample, the support layer 2010 can include silicon dioxide (SiO.sub.2),silicon nitride (SiN), or other like materials. In a specific example,this support layer 2010 can be deposited with a thickness of about 2-3um. As described above, other support layers (e.g., SiNx) can be used inthe case of a PSG sacrificial layer.

FIGS. 21A-21C are simplified diagrams illustrating variouscross-sectional views of a single crystal acoustic resonator device andof method steps for a transfer process using a sacrificial layer forsingle crystal acoustic resonator devices according to an example of thepresent invention. As shown, these figures illustrate the method step ofpolishing the support layer 2010 to form a polished support layer 2011.In an example, the polishing process can include a chemical-mechanicalplanarization process or the like.

FIGS. 22A-22C are simplified diagrams illustrating variouscross-sectional views of a single crystal acoustic resonator device andof method steps for a transfer process using a sacrificial layer forsingle crystal acoustic resonator devices according to an example of thepresent invention. As shown, these figures illustrate flipping thedevice and physically coupling overlying the support layer 2011overlying a bond substrate 2210. In an example, the bond substrate 2210can include a bonding support layer 2220 (SiO.sub.2 or like material)overlying a substrate having silicon (Si), sapphire (Al.sub.2O.sub.3),silicon dioxide (SiO.sub.2), silicon carbide (SiC), or other likematerials. In a specific embodiment, the bonding support layer 2220 ofthe bond substrate 2210 is physically coupled to the polished supportlayer 2011. Further, the physical coupling process can include a roomtemperature bonding process following by a 300 degree Celsius annealingprocess.

FIGS. 23A-23C are simplified diagrams illustrating variouscross-sectional views of a single crystal acoustic resonator device andof method steps for a transfer process using a sacrificial layer forsingle crystal acoustic resonator devices according to an example of thepresent invention. As shown, these figures illustrate the method step ofremoving the growth substrate 1610 or otherwise the transfer of thepiezoelectric thin film 1620. In an example, the removal process caninclude a grinding process, a blanket etching process, a film transferprocess, an ion implantation transfer process, a laser crack transferprocess, or the like and combinations thereof.

Further referring to FIGS. 23A-23C, the growth substrate 1610 can beremoved to expose the backside surface of the piezoelectric thin film1620. The exposed backside surface of the piezoelectric thin film 1620can also be processed to remove the first formed portions of thepiezoelectric thin film 1620. As appreciated by the present inventors,the portion of the piezoelectric thin film 1620 that is first formed (bysputtering, CVD, or other processes at high or low temperatures) canhave a lower crystalline quality that later formed portions.Accordingly, the first formed portion of the piezoelectric thin film1620 that contacted the growth substrate 1610 and the portionsimmediately adjacent to the first formed portion, can have a lowercrystalline quality than portions that were later formed.

As further appreciated by the present inventors, removing the portion ofthe piezoelectric thin film that was first formed on the growthsubstrate can eliminate the lower crystallinity portion of thepiezoelectric thin film such that the remaining portion of thepiezoelectric thin film 1620 has a higher crystallinity. For example, insome embodiments, a piezoelectric thin film of AlN or AlScN can beprocessed to remove about at least 500 Angstroms of material from theback-side of the film (the portion that was first formed on thesubstrate) so that the remaining portion has a crystallinity of lessthan about 1.0 degree at Full Width Half Maximum (FWHM) to about 10arcseconds at FWHM measured using X-ray diffraction (XRD). In someembodiments, the crystallinity of the piezoelectric thin film can be ina range between about 1.0 degree at FWHM to about 0.5 degrees at FWHMmeasured using XRD.

FIGS. 24A-24C are simplified diagrams illustrating variouscross-sectional views of a single crystal acoustic resonator device andof method steps for a transfer process using a sacrificial layer forsingle crystal acoustic resonator devices according to an example of thepresent invention. As shown, these figures illustrate the method step offorming an electrode contact via 2410 within the piezoelectric film 1620(becoming piezoelectric film 1621) overlying the first electrode 1710and forming one or more release holes 2420 within the piezoelectric film1620 and the first passivation layer 1810 overlying the sacrificiallayer 1910. The via forming processes can include various types ofetching processes.

FIGS. 25A-25C are simplified diagrams illustrating variouscross-sectional views of a single crystal acoustic resonator device andof method steps for a transfer process using a sacrificial layer forsingle crystal acoustic resonator devices according to an example of thepresent invention. As shown, these figures illustrate the method step offorming a second electrode 2510 overlying the piezoelectric film 1621.In an example, the formation of the second electrode 2510 includesdepositing molybdenum (Mo), ruthenium (Ru), tungsten (W), or other likematerials; and then etching the second electrode 2510 to form anelectrode cavity 2511 and to remove portion 2511 from the secondelectrode to form a top metal 2520. Further, the top metal 2520 isphysically coupled to the first electrode 1720 through electrode contactvia 2410.

FIGS. 26A-26C are simplified diagrams illustrating variouscross-sectional views of a single crystal acoustic resonator device andof method steps for a transfer process using a sacrificial layer forsingle crystal acoustic resonator devices according to an example of thepresent invention. As shown, these figures illustrate the method step offorming a first contact metal 2610 overlying a portion of the secondelectrode 2510 and a portion of the piezoelectric film 1621, and forminga second contact metal 2611 overlying a portion of the top metal 2520and a portion of the piezoelectric film 1621. In an example, the firstand second contact metals can include gold (Au), aluminum (Al), copper(Cu), nickel (Ni), aluminum bronze (AlCu), or related alloys of thesematerials or other like materials.

FIGS. 27A-27C are simplified diagrams illustrating variouscross-sectional views of a single crystal acoustic resonator device andof method steps for a transfer process using a sacrificial layer forsingle crystal acoustic resonator devices according to an example of thepresent invention. As shown, these figures illustrate the method step offorming a second passivation layer 2710 overlying the second electrode2510, the top metal 2520, and the piezoelectric film 1621. In anexample, the second passivation layer 2710 can include silicon nitride(SiN), silicon oxide (SiOx), or other like materials. In a specificexample, the second passivation layer 2710 can have a thickness rangingfrom about 50 nm to about 100 nm.

FIGS. 28A-28C are simplified diagrams illustrating variouscross-sectional views of a single crystal acoustic resonator device andof method steps for a transfer process using a sacrificial layer forsingle crystal acoustic resonator devices according to an example of thepresent invention. As shown, these figures illustrate the method step ofremoving the sacrificial layer 1910 to form an air cavity 2810. In anexample, the removal process can include a poly-Si etch or an a-Si etch,or the like.

FIGS. 29A-29C are simplified diagrams illustrating variouscross-sectional views of a single crystal acoustic resonator device andof method steps for a transfer process using a sacrificial layer forsingle crystal acoustic resonator devices according to another exampleof the present invention. As shown, these figures illustrate the methodstep of processing the second electrode 2510 and the top metal 2520 toform a processed second electrode 2910 and a processed top metal 2920.This step can follow the formation of second electrode 2510 and topmetal 2520. In an example, the processing of these two componentsincludes depositing molybdenum (Mo), ruthenium (Ru), tungsten (W), orother like materials; and then etching (e.g., dry etch or the like) thismaterial to form the processed second electrode 2910 with an electrodecavity 2912 and the processed top metal 2920. The processed top metal2920 remains separated from the processed second electrode 2910 by theremoval of portion 2911. In a specific example, the processed secondelectrode 2910 is characterized by the addition of an energy confinementstructure configured on the processed second electrode 2910 to increaseQ.

FIGS. 30A-30C are simplified diagrams illustrating variouscross-sectional views of a single crystal acoustic resonator device andof method steps for a transfer process using a sacrificial layer forsingle crystal acoustic resonator devices according to another exampleof the present invention. As shown, these figures illustrate the methodstep of processing the first electrode 1710 to form a processed firstelectrode 2310. This step can follow the formation of first electrode1710. In an example, the processing of these two components includesdepositing molybdenum (Mo), ruthenium (Ru), tungsten (W), or other likematerials; and then etching (e.g., dry etch or the like) this materialto form the processed first electrode 3010 with an electrode cavity,similar to the processed second electrode 2910. Air cavity 2811 showsthe change in cavity shape due to the processed first electrode 3010. Ina specific example, the processed first electrode 3010 is characterizedby the addition of an energy confinement structure configured on theprocessed second electrode 3010 to increase Q.

FIGS. 31A-31C are simplified diagrams illustrating variouscross-sectional views of a single crystal acoustic resonator device andof method steps for a transfer process using a sacrificial layer forsingle crystal acoustic resonator devices according to another exampleof the present invention. As shown, these figures illustrate the methodstep of processing the first electrode 1710, to form a processed firstelectrode 2310, and the second electrode 2510/top metal 2520 to form aprocessed second electrode 2910/processed top metal 2920. These stepscan follow the formation of each respective electrode, as described forFIGS. 29A-29C and 30A-30C. Those of ordinary skill in the art willrecognize other variations, modifications, and alternatives.

FIGS. 32A-32C through FIGS. 46A-46C illustrate a method of fabricationfor an acoustic resonator device using a transfer structure withoutsacrificial layer. In these figure series described below, the “A”figures show simplified diagrams illustrating top cross-sectional viewsof single crystal resonator devices according to various embodiments ofthe present invention. The “B” figures show simplified diagramsillustrating lengthwise cross-sectional views of the same devices in the“A” figures. Similarly, the “C” figures show simplified diagramsillustrating widthwise cross-sectional views of the same devices in the“A” figures. In some cases, certain features are omitted to highlightother features and the relationships between such features. Those ofordinary skill in the art will recognize variations, modifications, andalternatives to the examples shown in these figure series.

FIGS. 32A-32C are simplified diagrams illustrating variouscross-sectional views of a single crystal acoustic resonator device andof method steps for a transfer process for single crystal acousticresonator devices according to an example of the present invention. Asshown, these figures illustrate the method step of forming apiezoelectric film 3220 overlying a growth substrate 3210. In anexample, the growth substrate 3210 can include silicon (S), siliconcarbide (SiC), or other like materials. The piezoelectric film 3220 canbe an epitaxial film including aluminum nitride (AlN), gallium nitride(GaN), or other like materials. Additionally, this piezoelectricsubstrate can be subjected to a thickness trim. The piezoelectric thinfilm 3220 (with or without a seed layer) can be formed as describedabove in reference to FIGS. 16 and 60-64 in some embodiments.

FIGS. 33A-33C are simplified diagrams illustrating variouscross-sectional views of a single crystal acoustic resonator device andof method steps for a transfer process for single crystal acousticresonator devices according to an example of the present invention. Asshown, these figures illustrate the method step of forming a firstelectrode 3310 overlying the surface region of the piezoelectric film3220. In an example, the first electrode 3310 can include molybdenum(Mo), ruthenium (Ru), tungsten (W), or other like materials. In aspecific example, the first electrode 3310 can be subjected to a dryetch with a slope. As an example, the slope can be about 60 degrees.

FIGS. 34A-34C are simplified diagrams illustrating variouscross-sectional views of a single crystal acoustic resonator device andof method steps for a transfer process for single crystal acousticresonator devices according to an example of the present invention. Asshown, these figures illustrate the method step of forming a firstpassivation layer 3410 overlying the first electrode 3310 and thepiezoelectric film 3220. In an example, the first passivation layer 3410can include silicon nitride (SiN), silicon oxide (SiOx), or other likematerials. In a specific example, the first passivation layer 3410 canhave a thickness ranging from about 50 nm to about 100 nm.

FIGS. 35A-35C are simplified diagrams illustrating variouscross-sectional views of a single crystal acoustic resonator device andof method steps for a transfer process for single crystal acousticresonator devices according to an example of the present invention. Asshown, these figures illustrate the method step of forming a supportlayer 3510 overlying the first electrode 3310, and the piezoelectricfilm 3220. In an example, the support layer 3510 can include silicondioxide (SiO.sub.2), silicon nitride (SiN), or other like materials. Ina specific example, this support layer 3510 can be deposited with athickness of about 2-3 um. As described above, other support layers(e.g., SiNx) can be used in the case of a PSG sacrificial layer.

FIGS. 36A-36C are simplified diagrams illustrating variouscross-sectional views of a single crystal acoustic resonator device andof method steps for a transfer process for single crystal acousticresonator devices according to an example of the present invention. Asshown, these figures illustrate the optional method step of processingthe support layer 3510 (to form support layer 3511) in region 3610. Inan example, the processing can include a partial etch of the supportlayer 3510 to create a flat bond surface. In a specific example, theprocessing can include a cavity region. In other examples, this step canbe replaced with a polishing process such as a chemical-mechanicalplanarization process or the like.

FIGS. 37A-37C are simplified diagrams illustrating variouscross-sectional views of a single crystal acoustic resonator device andof method steps for a transfer process for single crystal acousticresonator devices according to an example of the present invention. Asshown, these figures illustrate the method step of forming an air cavity3710 within a portion of the support layer 3511 (to form support layer3512). In an example, the cavity formation can include an etchingprocess that stops at the first passivation layer 3410.

FIGS. 38A-38C are simplified diagrams illustrating variouscross-sectional views of a single crystal acoustic resonator device andof method steps for a transfer process for single crystal acousticresonator devices according to an example of the present invention. Asshown, these figures illustrate the method step of forming one or morecavity vent holes 3810 within a portion of the piezoelectric film 3220through the first passivation layer 3410. In an example, the cavity ventholes 3810 connect to the air cavity 3710.

FIGS. 39A-39C are simplified diagrams illustrating variouscross-sectional views of a single crystal acoustic resonator device andof method steps for a transfer process for single crystal acousticresonator devices according to an example of the present invention. Asshown, these figures illustrate flipping the device and physicallycoupling overlying the support layer 3512 overlying a bond substrate3910. In an example, the bond substrate 3910 can include a bondingsupport layer 3920 (SiO.sub.2 or like material) overlying a substratehaving silicon (Si), sapphire (Al.sub.2O.sub.3), silicon dioxide(SiO.sub.2), silicon carbide (SiC), or other like materials. In aspecific embodiment, the bonding support layer 3920 of the bondsubstrate 3910 is physically coupled to the polished support layer 3512.Further, the physical coupling process can include a room temperaturebonding process following by a 300 degree Celsius annealing process.

FIGS. 40A-40C are simplified diagrams illustrating variouscross-sectional views of a single crystal acoustic resonator device andof method steps for a transfer process for single crystal acousticresonator devices according to an example of the present invention. Asshown, these figures illustrate the method step of removing the growthsubstrate 3210 or otherwise the transfer of the piezoelectric film 3220.In an example, the removal process can include a grinding process, ablanket etching process, a film transfer process, an ion implantationtransfer process, a laser crack transfer process, or the like andcombinations thereof.

Further referring to FIGS. 40A-40C, the growth substrate 3210 can beremoved to expose the backside surface of the piezoelectric thin film3220. The exposed backside surface of the piezoelectric thin film 1620can also be processed to remove the first formed portions of thepiezoelectric thin film 1620. As appreciated by the present inventors,the portion of the piezoelectric thin film 3220 that is first formed (bysputtering, CVD, or other processes at high or low temperatures) canhave a lower crystalline quality that later formed portions.Accordingly, the first formed portion of the piezoelectric thin film3220 that contacted the growth substrate 3210 and the portionsimmediately adjacent to the first formed portion, can have a lowercrystalline quality than portions that were later formed.

As further appreciated by the present inventors, removing the portion ofthe piezoelectric thin film that was first formed on the growthsubstrate can eliminate the lower crystallinity portion of thepiezoelectric thin film such that the remaining portion of thepiezoelectric thin film 3220 has a higher crystallinity. For example, insome embodiments, a piezoelectric thin film of AlN or AlScN can beprocessed to remove about at least 500 Angstroms of material from theback-side of the film (the portion that was first formed on thesubstrate) so that the remaining portion has a crystallinity of lessthan about 1.0 degree at Full Width Half Maximum (FWHM) to about 10arcseconds at FWHM measured using X-ray diffraction (XRD). In someembodiments, the crystallinity of the piezoelectric thin film can be ina range between about 1.0 degree at FWHM to about 0.5 degrees at FWHMmeasured using XRD.

FIGS. 41A-41C are simplified diagrams illustrating variouscross-sectional views of a single crystal acoustic resonator device andof method steps for a transfer process for single crystal acousticresonator devices according to an example of the present invention. Asshown, these figures illustrate the method step of forming an electrodecontact via 4110 within the piezoelectric film 3220 overlying the firstelectrode 3310. The via forming processes can include various types ofetching processes.

FIGS. 42A-42C are simplified diagrams illustrating variouscross-sectional views of a single crystal acoustic resonator device andof method steps for a transfer process for single crystal acousticresonator devices according to an example of the present invention. Asshown, these figures illustrate the method step of forming a secondelectrode 4210 overlying the piezoelectric film 3220. In an example, theformation of the second electrode 4210 includes depositing molybdenum(Mo), ruthenium (Ru), tungsten (W), or other like materials; and thenetching the second electrode 4210 to form an electrode cavity 4211 andto remove portion 4211 from the second electrode to form a top metal4220. Further, the top metal 4220 is physically coupled to the firstelectrode 3310 through electrode contact via 4110.

FIGS. 43A-43C are simplified diagrams illustrating variouscross-sectional views of a single crystal acoustic resonator device andof method steps for a transfer process for single crystal acousticresonator devices according to an example of the present invention. Asshown, these figures illustrate the method step of forming a firstcontact metal 4310 overlying a portion of the second electrode 4210 anda portion of the piezoelectric film 3220, and forming a second contactmetal 4311 overlying a portion of the top metal 4220 and a portion ofthe piezoelectric film 3220. In an example, the first and second contactmetals can include gold (Au), aluminum (Al), copper (Cu), nickel (Ni),aluminum bronze (AlCu), or other like materials. This figure also showsthe method step of forming a second passivation layer 4320 overlying thesecond electrode 4210, the top metal 4220, and the piezoelectric film3220. In an example, the second passivation layer 4320 can includesilicon nitride (SiN), silicon oxide (SiOx), or other like materials. Ina specific example, the second passivation layer 4320 can have athickness ranging from about 50 nm to about 100 nm.

FIGS. 44A-44C are simplified diagrams illustrating variouscross-sectional views of a single crystal acoustic resonator device andof method steps for a transfer process for single crystal acousticresonator devices according to another example of the present invention.As shown, these figures illustrate the method step of processing thesecond electrode 4210 and the top metal 4220 to form a processed secondelectrode 4410 and a processed top metal 4420. This step can follow theformation of second electrode 4210 and top metal 4220. In an example,the processing of these two components includes depositing molybdenum(Mo), ruthenium (Ru), tungsten (W), or other like materials; and thenetching (e.g., dry etch or the like) this material to form the processedsecond electrode 4410 with an electrode cavity 4412 and the processedtop metal 4420. The processed top metal 4420 remains separated from theprocessed second electrode 4410 by the removal of portion 4411. In aspecific example, the processed second electrode 4410 is characterizedby the addition of an energy confinement structure configured on theprocessed second electrode 4410 to increase Q.

FIGS. 45A-45C are simplified diagrams illustrating variouscross-sectional views of a single crystal acoustic resonator device andof method steps for a transfer process using a sacrificial layer forsingle crystal acoustic resonator devices according to another exampleof the present invention. As shown, these figures illustrate the methodstep of processing the first electrode 3310 to form a processed firstelectrode 4510. This step can follow the formation of first electrode3310. In an example, the processing of these two components includesdepositing molybdenum (Mo), ruthenium (Ru), tungsten (W), or other likematerials; and then etching (e.g., dry etch or the like) this materialto form the processed first electrode 4510 with an electrode cavity,similar to the processed second electrode 4410. Air cavity 3711 showsthe change in cavity shape due to the processed first electrode 4510. Ina specific example, the processed first electrode 4510 is characterizedby the addition of an energy confinement structure configured on theprocessed second electrode 4510 to increase Q.

FIGS. 46A-46C are simplified diagrams illustrating variouscross-sectional views of a single crystal acoustic resonator device andof method steps for a transfer process using a sacrificial layer forsingle crystal acoustic resonator devices according to another exampleof the present invention. As shown, these figures illustrate the methodstep of processing the first electrode 3310, to form a processed firstelectrode 4510, and the second electrode 4210/top metal 4220 to form aprocessed second electrode 4410/processed top metal 4420. These stepscan follow the formation of each respective electrode, as described forFIGS. 44A-44C and 45A-45C. Those of ordinary skill in the art willrecognize other variations, modifications, and alternatives.

FIGS. 47A-47C through FIGS. 59A-59C illustrate a method of fabricationfor an acoustic resonator device using a transfer structure with amultilayer mirror structure. In these figure series described below, the“A” figures show simplified diagrams illustrating top cross-sectionalviews of single crystal resonator devices according to variousembodiments of the present invention. The “B” figures show simplifieddiagrams illustrating lengthwise cross-sectional views of the samedevices in the “A” figures. Similarly, the “C” figures show simplifieddiagrams illustrating widthwise cross-sectional views of the samedevices in the “A” figures. In some cases, certain features are omittedto highlight other features and the relationships between such features.Those of ordinary skill in the art will recognize variations,modifications, and alternatives to the examples shown in these figureseries.

FIGS. 47A-47C are simplified diagrams illustrating variouscross-sectional views of a single crystal acoustic resonator device andof method steps for a transfer process with a multilayer mirror forsingle crystal acoustic resonator devices according to an example of thepresent invention. As shown, these figures illustrate the method step offorming a piezoelectric film 4720 overlying a growth substrate 4710. Inan example, the growth substrate 4710 can include silicon (S), siliconcarbide (SiC), or other like materials. The piezoelectric thin film 4720can be an epitaxial film including aluminum nitride (AlN), galliumnitride (GaN), or other like materials. Additionally, this piezoelectricsubstrate can be subjected to a thickness trim. The piezoelectric thinfilm 4720 (with or without a seed layer) can be formed as describedabove in reference to FIGS. 60-64 in some embodiments.

FIGS. 48A-48C are simplified diagrams illustrating variouscross-sectional views of a single crystal acoustic resonator device andof method steps for a transfer process with a multilayer mirror forsingle crystal acoustic resonator devices according to an example of thepresent invention. As shown, these figures illustrate the method step offorming a first electrode 4810 overlying the surface region of thepiezoelectric film 4720. In an example, the first electrode 4810 caninclude molybdenum (Mo), ruthenium (Ru), tungsten (W), or other likematerials. In a specific example, the first electrode 4810 can besubjected to a dry etch with a slope. As an example, the slope can beabout 60 degrees.

FIGS. 49A-49C are simplified diagrams illustrating variouscross-sectional views of a single crystal acoustic resonator device andof method steps for a transfer process with a multilayer mirror forsingle crystal acoustic resonator devices according to an example of thepresent invention. As shown, these figures illustrate the method step offorming a multilayer mirror or reflector structure. In an example, themultilayer mirror includes at least one pair of layers with a lowimpedance layer 4910 and a high impedance layer 4920. In FIGS. 49A-49C,two pairs of low/high impedance layers are shown (low: 4910 and 4911;high: 4920 and 4921). In an example, the mirror/reflector area can belarger than the resonator area and can encompass the resonator area. Ina specific embodiment, each layer thickness is about ¼ of the wavelengthof an acoustic wave at a targeting frequency. The layers can bedeposited in sequence and be etched afterwards, or each layer can bedeposited and etched individually. In another example, the firstelectrode 4810 can be patterned after the mirror structure is patterned.

FIGS. 50A-50C are simplified diagrams illustrating variouscross-sectional views of a single crystal acoustic resonator device andof method steps for a transfer process with a multilayer mirror forsingle crystal acoustic resonator devices according to an example of thepresent invention. As shown, these figures illustrate the method step offorming a support layer 5010 overlying the mirror structure (layers4910, 4911, 4920, and 4921), the first electrode 4810, and thepiezoelectric film 4720. In an example, the support layer 5010 caninclude silicon dioxide (SiO.sub.2), silicon nitride (SiN), or otherlike materials. In a specific example, this support layer 5010 can bedeposited with a thickness of about 2-3 um. As described above, othersupport layers (e.g., SiNx) can be used.

FIGS. 51A-51C are simplified diagrams illustrating variouscross-sectional views of a single crystal acoustic resonator device andof method steps for a transfer process with a multilayer mirror forsingle crystal acoustic resonator devices according to an example of thepresent invention. As shown, these figures illustrate the method step ofpolishing the support layer 5010 to form a polished support layer 5011.In an example, the polishing process can include a chemical-mechanicalplanarization process or the like.

FIGS. 52A-52C are simplified diagrams illustrating variouscross-sectional views of a single crystal acoustic resonator device andof method steps for a transfer process with a multilayer mirror forsingle crystal acoustic resonator devices according to an example of thepresent invention. As shown, these figures illustrate flipping thedevice and physically coupling overlying the support layer 5011overlying a bond substrate 5210. In an example, the bond substrate 5210can include a bonding support layer 5220 (SiO.sub.2 or like material)overlying a substrate having silicon (Si), sapphire (Al.sub.2O.sub.3),silicon dioxide (SiO.sub.2), silicon carbide (SiC), or other likematerials. In a specific embodiment, the bonding support layer 5220 ofthe bond substrate 5210 is physically coupled to the polished supportlayer 5011. Further, the physical coupling process can include a roomtemperature bonding process following by a 300 degree Celsius annealingprocess.

FIGS. 53A-53C are simplified diagrams illustrating variouscross-sectional views of a single crystal acoustic resonator device andof method steps for a transfer process with a multilayer mirror forsingle crystal acoustic resonator devices according to an example of thepresent invention. As shown, these figures illustrate the method step ofremoving the growth substrate 4710 or otherwise the transfer of thepiezoelectric thin film 4720. In an example, the removal process caninclude a grinding process, a blanket etching process, a film transferprocess, an ion implantation transfer process, a laser crack transferprocess, or the like and combinations thereof.

Further referring to FIGS. 53A-53C, the growth substrate 4710 can beremoved to expose the backside surface of the piezoelectric thin film4720. The exposed backside surface of the piezoelectric thin film 4720can also be processed to remove the first formed portions of thepiezoelectric thin film 4720. As appreciated by the present inventors,the portion of the piezoelectric thin film 4720 that is first formed (bysputtering, CVD, or other processes at high or low temperatures) canhave a lower crystalline quality that later formed portions.Accordingly, the first formed portion of the piezoelectric thin film4720 that contacted the growth substrate 1610 and the portionsimmediately adjacent to the first formed portion, can have a lowercrystalline quality than portions that were later formed.

As further appreciated by the present inventors, removing the portion ofthe piezoelectric thin film that was first formed on the growthsubstrate can eliminate the lower crystallinity portion of thepiezoelectric thin film such that the remaining portion of thepiezoelectric thin film 4720 has a higher crystallinity. For example, insome embodiments, a piezoelectric thin film of AlN or AlScN can beprocessed to remove about at least 500 Angstroms of material from theback-side of the film (the portion that was first formed on thesubstrate) so that the remaining portion has a crystallinity of lessthan about 1.0 degree at Full Width Half Maximum (FWHM) to about 10arcseconds at FWHM measured using X-ray diffraction (XRD). In someembodiments, the crystallinity of the piezoelectric thin film can be ina range between about 1.0 degree at FWHM to about 0.5 degrees at FWHMmeasured using XRD.

FIGS. 54A-54C are simplified diagrams illustrating variouscross-sectional views of a single crystal acoustic resonator device andof method steps for a transfer process with a multilayer mirror forsingle crystal acoustic resonator devices according to an example of thepresent invention. As shown, these figures illustrate the method step offorming an electrode contact via 5410 within the piezoelectric film 4720overlying the first electrode 4810. The via forming processes caninclude various types of etching processes.

FIGS. 55A-55C are simplified diagrams illustrating variouscross-sectional views of a single crystal acoustic resonator device andof method steps for a transfer process with a multilayer mirror forsingle crystal acoustic resonator devices according to an example of thepresent invention. As shown, these figures illustrate the method step offorming a second electrode 5510 overlying the piezoelectric film 4720.In an example, the formation of the second electrode 5510 includesdepositing molybdenum (Mo), ruthenium (Ru), tungsten (W), or other likematerials; and then etching the second electrode 5510 to form anelectrode cavity 5511 and to remove portion 5511 from the secondelectrode to form a top metal 5520. Further, the top metal 5520 isphysically coupled to the first electrode 5520 through electrode contactvia 5410.

FIGS. 56A-56C are simplified diagrams illustrating variouscross-sectional views of a single crystal acoustic resonator device andof method steps for a transfer process with a multilayer mirror forsingle crystal acoustic resonator devices according to an example of thepresent invention. As shown, these figures illustrate the method step offorming a first contact metal 5610 overlying a portion of the secondelectrode 5510 and a portion of the piezoelectric film 4720, and forminga second contact metal 5611 overlying a portion of the top metal 5520and a portion of the piezoelectric film 4720. In an example, the firstand second contact metals can include gold (Au), aluminum (Al), copper(Cu), nickel (Ni), aluminum bronze (AlCu), or other like materials. Thisfigure also shows the method step of forming a second passivation layer5620 overlying the second electrode 5510, the top metal 5520, and thepiezoelectric film 4720. In an example, the second passivation layer5620 can include silicon nitride (SiN), silicon oxide (SiOx), or otherlike materials. In a specific example, the second passivation layer 5620can have a thickness ranging from about 50 nm to about 100 nm.

FIGS. 57A-57C are simplified diagrams illustrating variouscross-sectional views of a single crystal acoustic resonator device andof method steps for a transfer process with a multilayer mirror forsingle crystal acoustic resonator devices according to another exampleof the present invention. As shown, these figures illustrate the methodstep of processing the second electrode 5510 and the top metal 5520 toform a processed second electrode 5710 and a processed top metal 5720.This step can follow the formation of second electrode 5710 and topmetal 5720. In an example, the processing of these two componentsincludes depositing molybdenum (Mo), ruthenium (Ru), tungsten (W), orother like materials; and then etching (e.g., dry etch or the like) thismaterial to form the processed second electrode 5410 with an electrodecavity 5712 and the processed top metal 5720. The processed top metal5720 remains separated from the processed second electrode 5710 by theremoval of portion 5711. In a specific example, this processing givesthe second electrode and the top metal greater thickness while creatingthe electrode cavity 5712. In a specific example, the processed secondelectrode 5710 is characterized by the addition of an energy confinementstructure configured on the processed second electrode 5710 to increaseQ.

FIGS. 58A-58C are simplified diagrams illustrating variouscross-sectional views of a single crystal acoustic resonator device andof method steps for a transfer process with a multilayer mirror forsingle crystal acoustic resonator devices according to another exampleof the present invention. As shown, these figures illustrate the methodstep of processing the first electrode 4810 to form a processed firstelectrode 5810. This step can follow the formation of first electrode4810. In an example, the processing of these two components includesdepositing molybdenum (Mo), ruthenium (Ru), tungsten (W), or other likematerials; and then etching (e.g., dry etch or the like) this materialto form the processed first electrode 5810 with an electrode cavity,similar to the processed second electrode 5710. Compared to the twoprevious examples, there is no air cavity. In a specific example, theprocessed first electrode 5810 is characterized by the addition of anenergy confinement structure configured on the processed secondelectrode 5810 to increase Q.

FIGS. 59A-59C are simplified diagrams illustrating variouscross-sectional views of a single crystal acoustic resonator device andof method steps for a transfer process with a multilayer mirror forsingle crystal acoustic resonator devices according to another exampleof the present invention. As shown, these figures illustrate the methodstep of processing the first electrode 4810, to form a processed firstelectrode 5810, and the second electrode 5510/top metal 5520 to form aprocessed second electrode 5710/processed top metal 5720. These stepscan follow the formation of each respective electrode, as described forFIGS. 57A-57C and 58A-58C. Those of ordinary skill in the art willrecognize other variations, modifications, and alternatives.

In each of the preceding examples relating to transfer processes, energyconfinement structures can be formed on the first electrode, secondelectrode, or both. In an example, these energy confinement structuresare mass loaded areas surrounding the resonator area. The resonator areais the area where the first electrode, the piezoelectric layer, and thesecond electrode overlap. The larger mass load in the energy confinementstructures lowers a cut-off frequency of the resonator. The cut-offfrequency is the lower or upper limit of the frequency at which theacoustic wave can propagate in a direction parallel to the surface ofthe piezoelectric film. Therefore, the cut-off frequency is theresonance frequency in which the wave is traveling along the thicknessdirection and thus is determined by the total stack structure of theresonator along the vertical direction. In piezoelectric films (e.g.,AlN), acoustic waves with lower frequency than the cut-off frequency canpropagate in a parallel direction along the surface of the film, i.e.,the acoustic wave exhibits a high-band-cut-off type dispersioncharacteristic. In this case, the mass loaded area surrounding theresonator provides a barrier preventing the acoustic wave frompropagating outside the resonator. By doing so, this feature increasesthe quality factor of the resonator and improves the performance of theresonator and, consequently, the filter.

In addition, the top single crystalline piezoelectric layer can bereplaced by a polycrystalline piezoelectric film. In such films, thelower part that is close to the interface with the substrate has poorcrystalline quality with smaller grain sizes and a wider distribution ofthe piezoelectric polarization orientation than the upper part of thefilm close to the surface. This is due to the polycrystalline growth ofthe piezoelectric film, i.e., the nucleation and initial film haverandom crystalline orientations. Considering AlN as a piezoelectricmaterial, the growth rate along the c-axis or the polarizationorientation is higher than other crystalline orientations that increasethe proportion of the grains with the c-axis perpendicular to the growthsurface as the film grows thicker. In a typical polycrystalline AlN filmwith about a 1 um thickness, the upper part of the film close to thesurface has better crystalline quality and better alignment in terms ofpiezoelectric polarization. By using the thin film transfer processcontemplated in the present invention, it is possible to use the upperportion of the polycrystalline film in high frequency BAW resonatorswith very thin piezoelectric films. This can be done by removing aportion of the piezoelectric layer during the growth substrate removalprocess. Of course, there can be other variations, modifications, andalternatives.

While the above is a full description of the specific embodiments,various modifications, alternative constructions and equivalents may beused. As an example, the packaged device can include any combination ofelements described above, as well as outside of the presentspecification. Therefore, the above description and illustrations shouldnot be taken as limiting the scope of the present invention which isdefined by the appended claims.

What is claimed is:
 1. A method of forming an acoustic resonator device,the method comprising: sputtering onto a first surface of a substrate toprovide a piezoelectric thin film comprising AlN, AlScN, AlCrN, HfMgAlN,or ZrMgAlN on the first surface of the substrate while the first surfaceof the substrate is at a temperature in a range between 350 degreesCentigrade to 850 degrees Centigrade; processing a second surface of thesubstrate that is opposite the first surface of the substrate to providean exposed surface of the piezoelectric thin film from beneath thesecond surface of the substrate, wherein the exposed surface of thepiezoelectric thin film comprises a first crystalline quality portion ofthe piezoelectric thin film; removing a portion of the exposed surfaceof the piezoelectric thin film to access a second crystalline qualityportion of the piezoelectric thin film that is covered by the firstcrystalline quality portion of the piezoelectric thin film, wherein thesecond crystalline quality portion of the piezoelectric thin film has acrystallinity of less than 1.0 degree at Full Width Half Maximum (FWHM)to 10 arcseconds at FWHM measured using X-ray diffraction (XRD); andprocessing the second crystalline quality portion of the piezoelectricthin film to provide an acoustic resonator device on the secondcrystalline quality portion of the piezoelectric thin film.
 2. Themethod of claim 1 wherein removing the portion of the exposed surface ofthe piezoelectric thin film comprises removing 500 Angstroms of thepiezoelectric thin film to expose the second crystalline quality portionof the piezoelectric thin film.
 3. The method of claim 1 whereinprocessing the second surface of the substrate that is opposite thefirst surface of the substrate is preceded by: forming a first electrodeon the piezoelectric thin film; and forming a sacrificial layer on thefirst electrode.
 4. The method of claim 1 wherein the sputtering ontothe first surface of the substrate comprises heating the substrate to atemperature in a range between 400 degrees Centigrade to 600 degreesCentigrade.
 5. The method of claim 1 wherein the sputtering onto thefirst surface of the substrate comprises sputtering a seed layerincluding one or more of elements Al, Sc, Cr, Hf, Mg, or Zr directlyonto the first surface of the substrate to form a nucleation layer priorto formation of the piezoelectric thin film.
 6. The method of claim 5further comprising: sputtering the one or more of the elements onto thenucleation layer to form the piezoelectric thin film.
 7. The method ofclaim 1 wherein the second crystalline quality portion of thepiezoelectric thin film has a crystallinity in a range between 1.0degree at FWHM to 0.5 degrees at FWHM measured using XRD.
 8. A method offorming an acoustic resonator device, the method comprising: sputteringonto a first surface of a growth substrate to provide a piezoelectricthin film comprising AlN, AlScN, AlCrN, HfMgAlN, or ZrMgAlN on the firstsurface of the growth substrate; forming a first electrode on thepiezoelectric thin film; forming a multilayer mirror or a reflectorstructure on the first electrode; forming a support layer on themultilayer mirror or reflector structure; coupling a bond substrate tothe support layer; processing a second surface of the growth substratethat is opposite the first surface of the growth substrate to provide anexposed surface of the piezoelectric thin film from beneath the secondsurface of the growth substrate, wherein the exposed surface of thepiezoelectric thin film comprises a first crystalline quality portion ofthe piezoelectric thin film; removing a portion of the exposed surfaceof the piezoelectric thin film to access a second crystalline qualityportion of the piezoelectric thin film that is covered by the firstcrystalline quality portion of the piezoelectric thin film, wherein thesecond crystalline quality portion of the piezoelectric thin film has ahigher quality than the first crystalline quality portion of thepiezoelectric thin film; processing a surface of the second crystallinequality portion of the piezoelectric thin film to form a via that passesthrough the second crystalline quality portion of the piezoelectric thinfilm that exposes the first electrode; depositing a metal on the surfaceof the second crystalline quality portion of the piezoelectric thin filmand depositing the metal in the via to contact the first electrode; andprocessing the metal to form a first electrode contact on the surface ofthe second crystalline quality portion of the piezoelectric thin filmand to form a second electrode on the surface of the second crystallinequality portion of the piezoelectric thin film that is electricallyisolated from the first electrode contact.